Discrete 600V GaN-on-Si power switches are in the prior art. For example, the companies International Rectifier and Transphorm have cascode GaN switches which heterogeneously combine a low voltage Si MOSFET and a normally-on GaN switch in a package. However, the cascode technology used is not suitable for a GaN IC half bridge circuit.
The low switching loss of 600V GaN HEMTs (high electron mobility transistors) has enabled increasing the switching frequency to decrease the size and weight of power converters. However, GaN power converters in the prior art have been limited to a switching frequency of about 1 MHz due to inductor loss, because ferrites in inductors become lossy above about 1 MHz.
The University of Colorado (UC) has reported GaN converters at a switching frequency of 200 MHz. These GaN converters use air-core inductors, which are small and efficient at this high frequency; however, the switching voltages are limited to only about 25V. The UC GaN converters are built on an insulating substrate, so the converters have a low parasitic output capacitance, which is needed for an efficient zero voltage switching (ZVS) converter at high frequency. However, the insulating substrate used in these converters used is SiC, and 6-inch SiC substrates are very expensive.
Silicon (Si) has been the preferred substrate for GaN power electronics. However, there are problems of dynamic on-resistance, leakage current, parasitic output capacitance, and reliability for GaN-on-Si, and as discussed above the switching frequency of high power converters is limited to about 1 MHz by ferrite core inductor losses. Most of the power electronic industry operates at 10 to 100 kHz, and most of the power converters have inductances of the order of 10 nH.
What is needed is an improved power converter that can operate at high switching frequencies and high voltage. The embodiments of the present disclosure answer these and other needs.